In-plane Molecular Order of a Photo-oriented Polyamic Acid Film: Enhancement upon Thermal Imidization

Abstract

We have determined the in-plane molecular order of a polyamic acid (PAA) film irradiated with linearly polarized ultraviolet light (LPUVL), as well as that of the polyimide film obtained by thermally imidizing it. The PAA examined in this study contains azobenzene units in the backbone structure. The in-plane molecular order of the PAA and polyimide films was determined from the anisotropy in the polarized IR absorption of the phenyl C-C stretching vibration polarized along the backbone structure. We found that the photoinduced anisotropy in the in-plane molecular orientation was small, but it increased significantly after thermal imidization; i.e. the in-plane molecular order of the polyimide film was much greater than that of the PAA film. The enhancement of the in-plane molecular order was tentatively attributed to the crystallization of the film caused by thermal imidization

Photoinduced inclination of polyimide molecules containing azobenzene in the backbone structure

“…19,36 Thus we found that the first LPUVL exposure in the double UV exposure method induced a significantly large anisotropy in the in-plane molecular orientation. Now we turn to the experimental results for the D film.…”

Incorporation of azobenzene chromophore into poly(amide‐imide)

“…Many polyimides bearing azobenzene chromophores have been synthesized 13–17. In many cases, the incorporation of the chromophore in the polymeric chain is accomplished by the synthesis of a special monomer containing the chromophore and further copolymerized with commercial monomers to form the final polymer.…”